/*
Copyright 2021 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package oapi

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"time"

	v2 "k8s.io/autoscaler/cluster-autoscaler/cloudprovider/exoscale/internal/github.com/exoscale/egoscale/v2/api"
)

const (
	// DefaultPollingInterval represents the default polling interval used in Poller.
	DefaultPollingInterval = 3 * time.Second

	operationStatePending = "pending"
	operationStateSuccess = "success"
	operationStateFailure = "failure"
	operationStateTimeout = "timeout"
)

// PollFunc represents a function invoked periodically in a polling loop. It returns a boolean flag
// true if the job is completed or false if polling must continue, and any error that occurred
// during the polling (which interrupts the polling regardless of the boolean flag value).
// Upon successful completion, an interface descring an opaque operation can be returned to the
// caller, which will have to perform type assertion depending on the PollFunc implementation.
type PollFunc func(ctx context.Context) (bool, interface{}, error)

// Poller represents a poller instance.
type Poller struct {
	interval time.Duration
	timeout  time.Duration
}

// NewPoller returns a Poller instance.
func NewPoller() *Poller {
	return &Poller{
		interval: DefaultPollingInterval,
	}
}

// WithInterval sets the interval at which the polling function will be executed (default: 3s).
func (p *Poller) WithInterval(interval time.Duration) *Poller {
	if interval > 0 {
		p.interval = interval
	}

	return p
}

// WithTimeout sets the time out value after which the polling routine will be cancelled
// (default: no time out).
func (p *Poller) WithTimeout(timeout time.Duration) *Poller {
	if timeout > 0 {
		p.timeout = timeout
	}

	return p
}

// Poll starts the polling routine, executing the provided polling function at the configured
// polling interval. Upon successful polling, an opaque operation is returned to the caller, which
// actual type has to asserted depending on the PollFunc executed.
func (p *Poller) Poll(ctx context.Context, pf PollFunc) (interface{}, error) {
	if p.timeout > 0 {
		ctxWithTimeout, cancel := context.WithTimeout(ctx, p.timeout)
		defer cancel()
		ctx = ctxWithTimeout
	}

	ticker := time.NewTicker(p.interval)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			done, res, err := pf(ctx)
			if err != nil {
				return nil, err
			}
			if !done {
				continue
			}

			return res, nil

		case <-ctx.Done():
			return nil, ctx.Err()
		}
	}
}

// OperationPoller returns a PollFunc function which queries the state of the specified job.
// Upon successful job completion, the type of the interface{} returned by the PollFunc is a
// pointer to a Resource object (*Resource).
func OperationPoller(client ClientWithResponsesInterface, zone string, id string) PollFunc {
	return func(ctx context.Context) (bool, interface{}, error) {
		resp, err := client.GetOperationWithResponse(v2.WithZone(ctx, zone), id)
		if err != nil {
			return true, nil, err
		}
		if resp.StatusCode() != http.StatusOK {
			return true, nil, fmt.Errorf("unexpected response from API: %s", resp.Status())
		}

		switch *resp.JSON200.State {
		case operationStatePending:
			return false, nil, nil

		case operationStateSuccess:
			return true, resp.JSON200.Reference, nil

		case operationStateFailure:
			return true, nil, errors.New("job failed")

		case operationStateTimeout:
			return true, nil, errors.New("job timed out")

		default:
			return true, nil, fmt.Errorf("unknown job state: %s", *resp.JSON200.State)
		}
	}
}
